Use of Combined Observational- and Model-Derived Photochemical Indicators to Assess the O3-NOx-VOC System Sensitivity in Urban Areas

Edson Carrillo-Torres,Iván Hernández-Paniagua,Alberto Mendoza

doi:10.3390/atmos8020022

Edson Carrillo-Torres, Iván Hernández-Paniagua + Show 1 more

Open Access

https://doi.org/10.3390/atmos8020022

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Journal: Atmosphere	Publication Date: Jan 26, 2017
Citations: 25	License type: CC BY 4.0

Affiliation: Tecnológico de Monterrey

Abstract

Tropospheric levels of O3 have historically exceeded the official annual Mexican standards within the Monterrey Metropolitan Area (MMA) in NE Mexico. High-frequency and high-precision measurements of tropospheric O3, NOy, NO2, NO, CO, SO2, PM10 and PM2.5 were made at the Obispado monitoring site near the downtown MMA from September 2012 to August 2013. The seasonal cycles of O3 and NOy are driven by changes in meteorology and to a lesser extent by variations in primary emissions. The NOy levels were positively correlated with O3 precursors and inversely correlated with O3 and wind speed. Recorded data were used to assess the O3-Volatile Organic Compounds (VOC)-NOx system’s sensitivity through an observational-based approach. The photochemical indicator O3/NOy was derived from measured data during the enhanced O3 production period (12:00–18:00 Central Daylight Time (CDT), GMT-0500). The O3/NOy ratios calculated for this time period showed that the O3 production within the MMA is VOC sensitive. A box model simulation of production rates of HNO3 (PHNO3) and total peroxides (Pperox) carried out for O3 episodes in fall and spring confirmed the VOC sensitivity within the MMA environment. No significant differences were observed in O3/NOy from weekdays to weekends or for PHNO3/Pperox ratios, confirming the limiting role of VOCs in O3 production within the MMA. The ratified photochemical regime observed may allow the environmental authorities to revise and verify the current policies for air quality control within the MMA.

Highlights

Increased tropospheric levels of O3 can be harmful for human health, vegetation and built infrastructure [1,2,3]
No significant differences were observed in O3 /NOy from weekdays to weekends or for production rates of HNO3 (PHNO3) /Pperox ratios, confirming the limiting role of Volatile Organic Compounds (VOC) in O3 production within the Monterrey Metropolitan Area (MMA)
2017, 8, O3 mixing ratios is22observed by mid-summer 2013, which is likely caused by a high wind speed (WS) typical of early summer

Summary

Introduction

Increased tropospheric levels of O3 can be harmful for human health, vegetation and built infrastructure [1,2,3]. Due to the non-linearity of the O3 -VOC-NOx system, O3 production can be VOC sensitive when controlled by the input of VOCs and increase in response to increased. O3 production can be NOx -sensitive when NOx emissions govern the system, and O3 mixing ratios increase in response to increased NOx emissions, but remain constant to variations of VOCs [4,5,6]. Existing studies report changes in O3 production during the daytime and from weekdays to weekends from VOC- to NOx -sensitive regimes and vice versa within the same region as a result of changes in the emissions of precursors and meteorology [7,8,9,10,11]. Because the majority of existing policies to reduce the tropospheric levels of O3 within urban areas focus on reducing the emissions of precursors, their success depends

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